The King has praised the “truly remarkable courage” of the Ukrainian people, in a message marking the first anniversary of Russia’s invasion.
Charles, who earlier this month met with Ukraine’s president Volodymyr Zelenskyy, also said he hoped the outpouring of solidarity from across the world would bring “strength from the knowledge that, together, we stand united”.
“It has now been a year that the people of Ukraine have suffered unimaginably from an unprovoked full-scale attack on their nation,” he said in a statement.
“They have shown truly remarkable courage and resilience in the face of such human tragedy.
“The world has watched in horror at all the unnecessary suffering inflicted upon Ukrainians, many of whom I have had the great pleasure of meeting here in the UK and, indeed, across the world, from Romania to Canada.
“It is heartening that the United Kingdom, along with its allies, is doing everything possible to help at this most difficult time.
“Therefore, I can only hope the outpouring of solidarity from across the globe may bring not only practical aid, but also strength from the knowledge that, together, we stand united.”
The statement is the first major comment by a British Monarch on the Ukraine conflict.
His mother, the late Queen, avoided direct comments on political matters throughout her 70-year reign.
However, there was much speculation over a large bunch of flowers in the Ukrainian colours of blue and yellow that appeared when she met Canadian prime minister Justin Trudeau in March 2022.
She also offered her “warmest greetings” to mark Ukraine’s annual Independence Day in August last year, in what she described as “this most challenging year”.
Charles greeted the president with a wide smile and a warm handshake in Buckingham Palace’s 1844 Room, saying he was delighted to meet him.
“We’ve all been worried about you and thinking about your country for so long,” the King said.
On Friday, a defiant Zelenskyy said Ukrainians had proven themselves to be “invincible” as he attended a parade and memorial service out in the open in central Kyiv to mark a year since Russia’s invasion of Ukraine.
On a day of commemorations and defiance, the Ukrainian president presented awards in the capital outside St Sophia Cathedral to surviving soldiers and wives and daughters of fallen “heroes”.
He described the past year as one of “pain, sorrow, faith and unity”.
Earlier, the Ukraine leader, who has remained steadfast alongside his people in the resistance against Vladimir Putin’s invading forces, said in a video message: “We are ready for anything. We will defeat everyone.”
Sitting behind a desk and recalling how he addressed Ukrainians a year ago, he described 24 February, 2022 as “the longest day of our lives, the most difficult day in our recent history”.
“We woke up early and haven’t slept since,” he said.
In a separate tweet, he wrote: “On 24 February, millions of us made a choice. Not a white flag, but the blue and yellow one. Not fleeing, but facing. Resisting and fighting.
“It was a year of pain, sorrow, faith, and unity. And this year, we remained invincible.
“We know that 2023 will be the year of our victory!”
He posted his comments alongside a video reflecting on the first 12 months of the bloody conflict which has claimed the lives of tens of thousands of civilians.
It included footage of families torn apart and in tears, and the destruction of cities, as well as remembering the war dead.
However, it also hailed the “bravery” of the Ukrainian people against the invading forces, and looked ahead to a year of “hope, endurance and invincibility”.